Vibration Analysis and Fatigue Assessment of Floors.Part I:Human Rhythmic Activities

Structural problems associated with excessive vibration of building floor systems when subjected to human rhythmic activities have been frequent.In this context,this research work aims to develop an analysis methodology to evaluate the human comfort and assess the fatigue performance of steel-concrete composite floors when subjected to human rhythmic activities(aerobics).The investigated structural model corresponds to a steel-concrete floor with dimensions of 10 m×10 m and a total area of 100 m^(2).The numerical model developed for the dynamic analysis of the floor adopted the usual mesh refinement techniques present in finite element method(FEM)simulations implemented in the ANSYS program.The investigated floor dynamic response was calculated through the consideration of people practicing rhythmic activities on the structure,in order to verify the occurrence of excessive vibration and to assess the human comfort.The fatigue assessment is based on a linear cumulative damage rule through the use of the Rainflow-counting algorithm and S-N curves from traditional design codes.The results indicated that,in several analysed situations,the investigated floor presents excessive vibration and user’s discomfort.On the other hand,the structure service life values were higher than those proposed by the design codes,ensuring that the members,connections and joints will not fail by fatigue cracking.

Self-sustained firing activities of the cortical network with plastic rules in weak AC electrical fields

Both external and endogenous electrical fields widely exist in the environment of cortical neurons. The effects of a weak alternating current （AC） field on a neural network model with synaptic plasticity are studied. It is found that self-sustained rhythmic firing patterns, which are closely correlated with the cognitive functions, are significantly modified due to the self-organizing of the network in the weak AC field. The activities of the neural networks are affected by the synaptic connection strength, the exterrtal stimuli, and so on. In the presence of learning rules, the synaptic connections can be modulated by the external stimuli, which will further enhance the sensitivity of the network to the external signal. The properties of the external AC stimuli can serve as control parameters in modulating the evolution of the neural network.

Neurotoxicity of prenatal alcohol exposure on medullary pre-B?tzinger complex neurons in neonatal rats

Prenatal alcohol exposure disrupts the development of normal fetal respiratory function, but whether it perturbs respiratory rhythmical discharge activity is unclear. Furthermore, it is unknown whether the 5-hydroxytryptamine 2A receptor（5-HT2AR） is involved in the effects of prenatal alcohol exposure. In the present study, pregnant female rats received drinking water containing alcohol at concentrations of 0%, 1%, 2%, 4%, 8% or 10%（v/v） throughout the gestation period. Slices of the medulla from 2-day-old neonatal rats were obtained to record respiratory rhythmical discharge activity. 5-HT2 AR protein and m RNA levels in the pre-B？tzinger complex of the respiratory center were measured by western blot analysis and quantitative RT-PCR, respectively. Compared with the 0% alcohol group, respiratory rhythmical discharge activity in medullary slices in the 4%, 8% and 10% alcohol groups was decreased, and the reduction was greatest in the 8% alcohol group. Respiratory rhythmical discharge activity in the 10% alcohol group was irregular. Thus, 8% was the most effective alcohol concentration at attenuating respiratory rhythmical discharge activity. These findings suggest that prenatal alcohol exposure attenuates respiratory rhythmical discharge activity in neonatal rats by downregulating 5-HT2 AR protein and m RNA levels.

Differentiating rhythmic high-amplitude delta with superimposed(poly)spikes from extreme delta brushes:limitations of standardized nomenclature and implications for patient management

Background Following the standardized nomenclature proposed by the American Clinical Neurophysiology Society(ACNS),rhythmic high-amplitude delta activity with superimposed spikes(RHADS)can be reported as an extreme delta brush(EDB).The clinical implications of similar electrographic patterns being reported as RHADS versus EDB are important to highlight.We aim to review the electrographic characteristics of RHADS,evaluate whether RHADS is seen in other neurological disorders,and identify the similar and unique characteristics between RHADS and EDB to ultimately determine the most accurate way to differentiate and report these patterns.We believe that the differentiation of RHADS and EDB is important as there is a vast difference in the diagnostic approach and the medical management of associated underlying etiologies.Data source We conducted an extensive search on MEDLINE and Pubmed utilizing various combinations of keywords.Searching for“gamma polymerase and EEG”,or“RHADS”or“Alpers syndrome and EEG”or“EEG”AND“Alpers–Huttenlocher syndrome”.Results Three articles were found to be focused on the description of“RHADS”pattern in Alpers Syndrome.No publication to date were found when searching for the terms“EDB”AND“children”,AND“infant”AND“adolescent”excluding“encephalitis”and“neonate”.Although RHADS and EDB appear as similar EEG patterns,meticulous analysis can differentiate them.RHADS is not exclusive to patients with Alpers–Huttenlocher syndrome and may manifest in regions beyond the posterior head region.Reactivity to eye-opening and response to anesthesia can be two other elements that help in the differentiation of these patterns.Conclusion RHADS is not exclusive to patients with AHS and may manifest in regions beyond the posterior head region.Reactivity to eye-opening and response to anesthesia are features that help in the differentiation of these patterns.